Internal combustion engine manufacturers are constantly seeking to increase power output and fuel efficiency of their products. One approach to generally increasing efficiency and power is to reduce the oscillating mass of an internal combustion engine, e.g., of the pistons, connecting rods, and other moving parts of the engine. Engine power may also be increased by raising the compression ratio of the engine. Raising the compression ratio of an engine also generally raises the pressure and temperature within the combustion chamber during operation.
As a result of the weight reductions in combination with increased pressures and temperatures associated with operation, engines, and in particular the pistons of the engine, are under increased stress. Piston cooling is therefore increasingly important for withstanding the increased stress of such operational conditions over the life of the engine.
To reduce the operating temperatures of piston components, a cooling gallery may be provided about a perimeter of the piston. A coolant such as crankcase oil may be introduced to the cooling gallery, and may be distributed about the cooling gallery by the reciprocating motion of the piston, thereby reducing the operating temperature of the piston.
At the same time, the cooling galleries may increase overall complexity of the piston assembly and manufacturing of the same. For example, cooling galleries may require additional component, such as a cooling gallery cover, to encourage proper circulation of a coolant throughout the cooling gallery by temporarily retaining coolant (e.g., oil) that is circulated through the cooling gallery. The additional components such as cover plates also add complexity, however. Additionally, cooling galleries may be expensive and/or difficult to form in smaller piston applications such as in the case of lightweight or light duty pistons.
Accordingly, there is a need for a piston that is practical for production in a mass manufacturing environment, while also allowing adequate cooling, such as by providing a cooling gallery.